How to pass “NULL” value into nullable field during call from JavaScript to ASP.NET WebService

Question

How to pass "NULL" value into nullable field during call from JavaScript to ASP.NET WebService?

I call method in the following way from JavaScript:

ws_data.SaveTasks(eval({"MyValue":"null"}), OnSaveComplete, OnError, OnTimeOut);

When I do, I receive an error (framework calls OnError):

null is not a valid value for Int32

If instead of "null" I pass valid integer - everything works fine.

Please advise: What I do wrong? How to pass 'null' value which will be 'translated' into a NULL .NET object?

Any ideas are welcome!

PS Here are some details.

Declaration of essential part of MyData:

public class MyData
{
    ...
    public int? MyValue { get; set; }
}

Declaration of ASP.NET web service:

[WebService(Namespace = "...")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
public class ws_data : WebService
{
    [WebMethod(true)]
    public object SaveData(MyData data)
    {...}
}

And ws_data is declared via ScriptManager:

    <asp:ScriptManager runat="server">
        <Services>
            <asp:ServiceReference Path="/ws_data.asmx" />
        </Services>
    </asp:ScriptManager>

Answer 1

This is because you're passing the string null instead of the non-value null. Remove the quotes to make it an actual null.

{"MyValue": null}

I'm not sure about your eval either, I think it can be omitted as eval is supposed to take a string an interpret it as JavaScript.

ws_data.SaveTasks({"MyValue": null}, OnSaveComplete, OnError, OnTimeOut);